Well, it's arguably a 380X replacement, too.
4GB is a good buy at current prices though, definitely.
8GB is still a good buy, but at £45 more, it doesn't have nearly the same value factor going for it. Which is a shame as it's going to be the card many will prefer to have.
In the end, it's still a jump in performance/price ratio, just maybe not what a lot of us were hoping for a 1.5x node jump plus new architecture. Looking a lot like outside of DX12 titles, you're going to need a decent OC on a 480 to match a decently OC'd 970. So question is - how much are those going to cost and does the value factor remain?
I do think people should stop saying, "Oh but you can get a 970 now for £220, this card is worthless!". Those prices are only because of the 480 coming in. It's like when the 970 came out and 780Ti's were reduced to £300 or so and arguing, "What's the point of the 970, you can get a 780Ti for £300!", ya know? It's a discontinued card at this point, not a viable option going into the future.
I do wonder if AMD haven't made for a reasonably easy performance target for Nvidia to match/beat with GP106 now.